Rick,
That's a hard question to answer. HP would have some dependance on what type of intake and or fuel system your running. Carburator or fuel injection. Times would depend on the weight of your car, and traction. I can take a wild guess and say mid 13's to lmid 14's assuming things are set up right.
Don't forget you will need a stall with that comp 280, I'm pretty sure they are ground on 110 lobe seperation angle and it will not have that great of vacuum. The 3.73 gears aren't that bad for the street, but if you plan on going to the track mostly I would go with a 4.10, you can go a with the higher ratios with that 5 speed since you will have overdrive. Good luck, hope everything works out for you with your project.